With the increasing demands of commercial mm-wave application such as Collision Avoidance Radar and Local Multi-points Distribution System (LMDS), a multi-layered large-scale array antenna has attracted some attention due to its flexibility in manufacturing, the capability of passive integration, and the low production cost. One potential application is to build a microstrip patch array antenna in a multilayer ceramic substrate. However, operating at mm-wave frequencies, a conventional microstrip patch array antenna on multilayer ceramic substrate would be less attractive because of its low element radiation efficiency and the loss from feeding network, which are caused by the relative high dielectric constant of a ceramic substrate.
Moreover, the bandwidth of a traditional patch antenna is proportional to the substrate thickness. To achieve a wider bandwidth, a thicker substrate can be used. However, working with the high dielectric constant substrate, a thicker substrate will lead to a higher surface wave loss and consequently degrade the radiation efficiency. For example, an antenna capable of achieving a 4% 2:1 VSWR bandwidth about 29 GHz on Dupont® 943 LTCC substrate (with dielectric constant of 7.5, a loss tangent of 0.002, and a thickness of 0.447 mm), the simulated radiation efficiency using IE3D™, is less than 78%.
It would, therefore, be desirable to provide an array antenna having relatively high radiation efficiency and relatively low cost.
The references cited herein are explicitly incorporated by reference in its entity.